Fatty acids have an essential role in a variety of cellular processes including building blocks for membranes, anchors for targeting membrane proteins, precursors in the synthesis of lipid second messengers and as a medium to store energy, (Menendez J S and Lupu R, Fatty acid synthase and the lipogenic phenotype in cancer pathogenesis, Nature Reviews Cancer, 7: 763-777 (2007)). Fatty acids can either be obtained from the diet or can be synthesized de novo from carbohydrate precursors. The biosynthesis of the latter is catalyzed by the multi-functional homodimeric FAS. FAS synthesizes long chain fatty acids by using acetyl-CoA as a primer and Malonyl Co-A as a 2 carbon donor, and NADPH as reducing equivalents (Wakil S J, Lipids, Structure and function of animal fatty acid synthase, 39: 1045-1053 (2004), Asturias F J et al., Structure and molecular organization of mammalian fatty acid synthase, Nature Struct. Mol. Biol. 12:225-232 (2005), Maier T, et al., Architecture of Mammalian Fatty Acid Synthase at 4.5 Å Resolution, Science 311:1258-1262 (2006)).
De novo fatty acid synthesis is active during embryogenesis and in fetal lungs where fatty acids are used for the production of lung surfactant. In adults, most normal human tissues preferentially acquire fatty acids from the diet. Therefore, the level of de novo lipogenesis and expression of lipogenic enzymes is low (Weiss L, et al., Fatty-acid biosynthesis in man, a pathway of minor importance. Purification, optimal assay conditions, and organ distribution of fatty-acid synthase. Biological Chemistry Hoppe-Seyler367(9):905-912 (1986)). In contrast, many tumors have high rates of de novo fatty acid synthesis (Medes G, et al., Metabolism of Neoplastic Tissue. IV. A Study of Lipid Synthesis in Neoplastic Tissue Slices in Vitro, Can Res, 13:27-29, (1953)). FAS has now been shown to be over-expressed in numerous cancer types including prostate, ovary, colon, endometrium, lung, bladder, stomach and kidney (Kuhajda F P, Fatty-acid synthase and human cancer: new perspectives on its role in tumor biology, Nutrition; 16:202-208 (2000)). This differential expression and function of FAS in tumors and normal cells provide an approach for cancer therapy with the potential of a substantial therapeutic window.
Pharmacological and small interference RNA mediated inhibition of FAS has demonstrated a preferential inhibition of cancer cell proliferation. Additionally, these inhibitors induce apoptosis in cancer cells in vitro and retard growth in human tumors in murine xenograft models in vivo (Menendez J S and Lupu R, Nature Reviews Cancer, 7: 763-777 (2007)). Based upon these findings, FAS is considered a major potential target of anti-neoplastic intervention.